The invention is generally related to inner rotor DC motors, particularly electronically-commutated, brushless direct current (DC) motors. Motors of this kind can be used in a variety of applications, examples being in automotive engineering for fans, cooling pumps or steering system support. Other application areas include ventilator fans in power supply units, or spindle motors in disk drives for data processing systems, just to mention a few.
A brushless DC motor basically consists of a shaft, a rotor assembly equipped with one or more permanent magnets arranged on the shaft, and a stator assembly which incorporates a stator component (e.g. made of sheet metal) and phase windings. Two bearings are mounted at an axial distance to each other on the shaft to support the rotor assembly and stator assembly relative to each other.
An example of a stator component which can be utilized in the stator assembly is illustrated in FIG. 1. The stator component 8 consists of a ring-shaped stator coil flux guide 10 and several pole shoes 12 which extend inwardly from the central, inner opening of the stator coil flux guide 10 in a radial direction. Stator slots 14 are formed between the pole shoes 12.
The stator component illustrated in the example in FIG. 1 has 27 pole shoes 12. Nine pole shoes 12 are available for each phase winding, as it is assumed that the stator component 8 is intended for a three-phase DC motor. A conflict arises in relation to the winding of the stator component 8 with three phase windings, as there must be sufficient space for applying the windings between the pole shoes 12, and a narrow opening 16 of the slot 14 is advantageous for the electromagnetic configuration of the stator. This conflict can be clearly seen in FIG. 1. It is increased by the fact that the space available for the winding between two pole shoes 12 actually is reduced by a tapered area which is required for inserting the winding wire between each two pole shoes 12.
The document DE 101 06 717 A1 describes an element for an electrical motor which can be used as a stator or rotor and consists of two supporting components which, when combined in an axial direction, form the element itself. Each of the supporting components has pole teeth, although directly adjacent pole teeth in the circumferential direction are not formed by the same supporting component to enable making of the distance between the adjacent teeth of the same supporting component large enough to considerably facilitate the winding procedure or the fitting of a coil.
Therefore it is the object of the invention to specify a stator component for an inner rotor motor which has a narrow slot opening to ensure good motor function, but simultaneously can be easily and efficiently wound.